RHEL 7 Service masking.

Many people don’t figure out why a Systemd service can be masked. They understand the need to enable it at boot and start it but why masking it?
Back to basics, a Systemd service can be:

manually started with the systemctl start command,

automatically started at boot with the systemctl enable command,

dbus-activated by another Systemd service (NetworkManager can be triggered like this),

socket-activated by some network activities (the printer service cups is a good example).

With this in mind, it becomes clear that masking a Systemd service with the systemctl mask command makes sense for a dbus-activated or a socket-activated service because in these cases stopping or disabling won’t definitively be enough!

Conclusion: If you want to be sure that a service will not start, mask it!